The present invention relates to devices utilizable in different types of breathing systems, such as those for administering anesthetic gases, or for the administration of oxygen to patients.
In recent years a number of improvements have been evolved for use in the practice of inhalation anesthetic administration. These improvements include: the two tube circle circuit disclosed in U.S. Pat. No. 3,556,097; the unilimb device and the anesthesia breathing system disclosed in U.S. Pat. No. 4,007,737; the anesthetic system described in the article entitled "A Streamline Anesthetic System" J. A. Bain and W. E. Sporel, which appears in Volume 19, No. 4 at page 426 of the Canadian Anesthetic Society Journal (July 1972), and the tube device of which is disclosed in U.S. Pat. No. 3,856,051 granted Dec. 24, 1974; and the system described by Drs. S. Ramanathan, Chalon, and Turndorf in an article entitled "A Compact, Well-Humidified Breathing Circuit For the Circle System" which appeared in Volume 44, No. 3 commencing at page 238 of the March 1976 issue of Anesthesiology.
Among such and other well-known breathing systems, that most commonly used is probably the circle circuit, orginally introduced in 1926 and an improvement of which is disclosed in U.S. Pat. No. 3,556,097 mentioned above. The principal problem in utilizing a circle circuit of such design arises from the use of two flexible tubes. Such tubes can impede the surgeon who may be confronted with having to operate in the vicinity of the head and neck of the patient. In addition, the same sized flexible tubes used in a circuit system for adults, cannot be employed for infants. Instead a miniaturized pair of flexible tubes must be utilized for the latter. While the rebreathing system described by Drs. Bain and Sporel in the article, and his pipe disclosed in said U.S. Pat. No. 3,856,051, mentioned above, have certain advantages from the standpoint of ease in the application to the patient and handling, the particular circuit is not generally regarded as efficient with regard to fresh gas economics during spontaneous breathing. Nor would the fresh gas tube of the said patent support such breathing. This pipe is, therefore, limited in its usage to the Bain and Sporel rebreathing system which has not been generally accepted to replace the circle circuit system.
In an effort to overcome the physical problems presented by the use of two flexible tubes or hoses in the manner illustrated in U.S. Pat. No. 3,556,097, both the patentee of U.S. Pat. No. 4,007,737 and Drs. Ramanathan, Chalon, and Turndorf have illustrated and described unilimb devices utilizable in a circle circuit system.
Although the unilimb devices thus suggested by prior researchers in this field have offered advantages over the two tube or hose system previously used in a circle circuit system, there are certain critical aspects in such prior unilimb devices which can present problems in certain applications therefor and/or which may otherwise limit their use to special situations. For example, although the unilimb of U.S. Pat. No. 4,007,737 is designed to minimize dead air space in a circle circuit breathing system, it does so by providing two one way valves in the terminal connector adapted for attachment to the mouth piece or other inlet means to the patient's respiratory system. Since any malfunction of either one-way valve could have a most serious, if not fatal, consequence, it becomes highly desireable to eliminate such valves altogether in this location. Further, by providing spacers between the inner and outer tubes in order to maintain them in a concentric disposition, the unilimb of the last-mentioned patent can develop undesireable gas flow impediments when the tubes become twisted.
While the clinical report by Drs. Ramanathan et al. does illustrate the use of a unilimb flexible tube or hose system between the source of the gas and the patient, insufficient details of the patient end of the device are disclosed to enable one skilled in the art to determine its exact physical structure.
Prior art devices of these types, moreover, appear to have been designed and utilizable only for particular applications. Thus, for example, a unilimb device for a circle circuit has had no utility in the rebreathing system described by Drs. Bain and Sporel in the article heretofore referenced. conversely, no device specifically designed for use in a rebreathing system, has heretofore been employable in a circle circuit system.
Additionally, prior art devices have been structured for a particular application and with fixed physical characteristics e.g. to provide a predetermined volume of dead air space, thus limiting the use of the device to the specific application for which the device may have been designed. Hence, if, for example, it should become desireable in the circle circuit to provide more or less dead air space than a given unilimb device is designed to provide, it has been necessary heretofore to have a new unilimb device designed and fabricated for such other specific application.
It has also been the observation of the present inventor that such unilimb prior art devices as have heretofore been described in any of the references, such as those hereinabove mentioned, have not been found particularly practicable from the standpoint of being readily manufacturable at a reasonable cost. This would appear to be particularly the situation with respect to the device of U.S. Pat. No. 4,007,737 with its one-way valve system and spacers for maintaining concentric disposition of the inner tube with respect to the outer tube.
If the cost of manufacturing such devices should prove too great, there will be considerable reluctance on the part of hospitals and other potential users of the devices to purchase the same, and particularly to discard them where such discard might become necessary or desireable after use with a patient which may have some type of communicable disease. Prior unilimb devices moreover have not heretofore been constructed in such a manner as to be easily disassemblable for cleaning sterilization or other type of servicing.
Thus, the devices of the prior art have not proved to be satisfactory from the standpoints of their fabrication, their servicing, their disposability, their utility, nor their adaptability for use in different systems, or for different applications in the same system.